The present invention relates to hermetic compressors and particularly to compressors having substantially horizontal drive shafts.
Hermetic compressors generally include a hermetically sealed housing in which a compression mechanism and an electric motor are disposed. The motor is coupled to the compression mechanism via a drive shaft. A substantially horizontal hermetic compressor is one in which the shaft axis of rotation and thus the drive shaft of the compressor are nearly horizontal. Electrical power is provided to the motor through a hermetic terminal assembly to induce rotation of the drive shaft. Rotation of the drive shaft induces rotation of the compression mechanism to compress refrigerant fluid in the compression mechanism and discharge refrigerant gas to a refrigeration system.
In horizontal compressors, the weight of the drive shaft and the rotor does not urge the drive shaft along its axis of rotation into a position in which the drive shaft is in abutting relationship with a thrust bearing surface. During operation of the compressor, the rotation of the rotor, drive shaft, and compression mechanism may generate oscillating axial movement of the drive shaft. Objectionable noise, such as knocking, often accompanies such back and forth oscillation of the drive shaft.
One method of biasing the rotor and the drive shaft in one direction along the longitudinal axis of rotation is by using the solenoid effect of the motor. The stator and the rotor of the motor are offset by a specific distance, and upon energization of the stator the rotor is urged in a direction to allow alignment of its laminae with those of the stator. The rotor exerts an axial force on the drive shaft, moving the drive shaft into engagement with a thrust bearing surface to maintain axial compliance of the drive shaft during compressor operation. Axial positioning of the rotor and stator must be closely toleranced.
Another method which may be employed to prevent axial oscillations of the drive shaft is to construct the compressor to have close tolerances and selective fits. This limits the available space in which the drive shaft may move and thereby limits axial movement of the drive shaft. By limiting the axial movement of the drive shaft, the amount of noise produced by oscillating axial movement of the drive shaft is reduced.
A problem with these methods of providing axial compliance of a horizontal drive shaft is that gaging and selective assembly of compressor components is labor intensive. Further, manufacturing processes for compressor components having close tolerances are more difficult and thus more expensive.
It is desirable to provide a shaft axial compliance mechanism for a substantially horizontal hermetic compressor which avoids selective fits and close tolerances to prevent objectionable noise created by oscillating axial movement of the drive shaft during compressor operation.
The present invention provides a shaft compliance mechanism for a substantially horizontal hermetic compressor to prevent objectionable noise created by oscillating axial movement of the drive shaft without resorting to close machining tolerances or selective assembly of components.
The drive shaft of a substantially horizontal hermetic compressor is provided with a circumferential groove near one end of the shaft. A bore is provided in the outboard bearing of the compressor which is aligned with the circumferential groove in the drive shaft. A retaining element such as a ball or an elongated pin is placed in the bore such that a portion of the retaining element is located within the bore and a portion of the retaining element is located in the shaft circumferential groove to prevent relative axial movement of the drive shaft.
The present invention provides a hermetic compressor assembly including a housing having mounted therein a compression mechanism and a motor which are operatively coupled by a drive shaft having a substantially horizontal axis of rotation. A bearing is disposed in the housing, is fixed relative to the compression mechanism and is disposed about the drive shaft. The drive shaft is provided with a circumferential groove in the outer surface thereof. A drive shaft retaining element is located in a bore located in the bearing with a first portion of the retaining element engaging the bore, and a second portion of the retaining element received in and engaging the circumferential groove. Relative movement of the drive shaft in both directions along the drive shaft axis of rotation is thereby prevented.
The present invention also provides a hermetic compressor assembly including a housing having a compression mechanism and a motor disposed therein. A drive shaft having an axis of rotation which is substantially horizontal operatively couples the compression mechanism and the motor. A bearing is disposed in the housing, is fixed relative to the compression mechanism and is disposed about the drive shaft. Further provided are means for engaging the drive shaft and the bearing to prevent relative movement between the compression mechanism and the drive shaft in both directions along the drive shaft axis of rotation.
The present invention also provides a hermetic compressor assembly including a housing having disposed therein a compression mechanism and a motor operatively coupled by a drive shaft. The drive shaft, having an axis of rotation which is substantially horizontal, has an outer surface in which a circumferential groove is provided. A bearing is disposed in the housing, is fixed relative to the compression mechanism and is disposed about the drive shaft. A ball is retained in a bore provided in the bearing such that a portion of the ball is received in and engages the shaft circumferential groove to prevent relative movement between the compression mechanism and the drive shaft in both directions along the drive shaft axis of rotation.
The present invention also provides a hermetic compressor assembly including a housing having disposed therein a compression mechanism and a motor operatively coupled by a drive shaft. The drive shaft has an outer surface in which a circumferential groove is provided and an axis of rotation which is substantially horizontal. A bearing is disposed in the housing, is fixed relative to the compression mechanism and is disposed about the drive shaft. The bearing is provided with a bore in which a pin is received. A portion of the pin is received in and engages the shaft circumferential groove to prevent relative movement between the compression mechanism and the drive shaft in both directions along the drive shaft axis of rotation.
The present invention provides a method of preventing oscillating axial movement of a substantially horizontal drive shaft during operation of a hermetic compressor. The method includes forming a circumferential groove in the drive shaft and rotatably supporting the drive shaft in a bearing. Further included is forming a bore in the bearing and aligning the bore and the circumferential groove. The method also includes engaging the bore and the circumferential groove each with a portion of a retaining element.
One advantage provided by the shaft axial compliance mechanisms of the present invention is that the tolerances of the compressor may be looser and selective component assembly is not required to provide axial compliance of the horizontal drive shaft. Further, the inventive axial compliance mechanism may be incorporated with only minor design and process revisions, and with only minimal increases in labor.